smb: fix post-trunc chunk behavior

After a gap in a file transaction, the file tracker is truncated. However
this did not clear any stored out of order chunks from memory or stop more
chunks to be stored, leading to accumulation of a large number of chunks.

This patches fixes this be clearing the stored chunks on trunc. It also
makes sure no more chunks are stored in the tracker after the trunc.

Bug: #5781.
(cherry picked from commit a24d7dc)

rust/src/filetracker.rs

@@ -120,6 +120,9 @@ impl FileTransferTracker {
         files.file_close(&self.track_id, myflags);
         SCLogDebug!("truncated file");
         self.file_is_truncated = true;
+        self.chunks.clear();
+        self.in_flight = 0;
+        self.cur_ooo = 0;
     }
 
     pub fn create(&mut self, _name: &[u8], _file_size: u64) {
@@ -157,6 +160,9 @@ impl FileTransferTracker {
         self.fill_bytes = fill_bytes;
         self.chunk_is_last = is_last;
 
+        if self.file_is_truncated {
+            return 0;
+        }
         if self.file_open == false {
             SCLogDebug!("NEW CHUNK: FILE OPEN");
             self.track_id = *xid;
@@ -176,6 +182,11 @@ impl FileTransferTracker {
     /// If gap_size > 0 'data' should not be used.
     /// return how much we consumed of data
     pub fn update(&mut self, files: &mut FileContainer, flags: u16, data: &[u8], gap_size: u32) -> u32 {
+        if self.file_is_truncated {
+            let consumed = std::cmp::min(data.len() as u32, self.chunk_left);
+            self.chunk_left = self.chunk_left.saturating_sub(data.len() as u32);
+            return consumed;
+        }
         let mut consumed = 0 as usize;
         let is_gap = gap_size > 0;
         if is_gap || gap_size > 0 {